"If a legal rule requires the facts to be proved (a 'fact in issue') a judge must decide whether or not it happened. There is no room for a finding that it might have happened. The law operates a binary system in which the only values are 0 and 1." 38. Third, findings of fact in these cases must be based on evidence. As Munby LJ, as he then was, observed in Re A (A Child) (Fact-finding hearing: Speculation) [2011]EWCA Civ 12: "
"Evidence cannot be evaluated and assessed in separate compartments. A judge in these difficult cases must have regard to the relevance of each piece of evidence to other evidence and to exercise an overview of the totality of the evidence in order to come to the conclusion whether the case put forward by the local authority has been made out to the appropriate standard of proof." 40. Fifthly, amongst the evidence received in this case, as is invariably the case in proceedings involving allegations of non-accidental head injury, is expert medical evidence from a variety of specialists. Whilst appropriate attention must be paid to the opinion of medical experts, those opinions need to be considered in the context of all the other evidence. The roles of the court and the expert are distinct. It is the court that is in the position to weigh up expert evidence against the other evidence (see A County Council & K, D, & L[2005] EWHC 144 (Fam) ;[2005] 1 FLR 851 per Charles J). Thus there may be cases, if the medical opinion evidence is that there is nothing diagnostic of non-accidental injury, where a judge, having considered all the evidence, reaches the conclusion that is at variance from that reached by the medical experts. 41. Sixth, in assessing the expert evidence I bear in mind that cases involving an allegation of shaking involve a multi-disciplinary analysis of the medical information conducted by a group of specialists, each bringing their own expertise to bear on the problem. The court must be careful to ensure that each expert keeps within the bounds of their own expertise and defers, where appropriate, to the expertise of others (see observations of King J in Re S[2009] EWHC 2115 Fam). 42. Seventh, the evidence of the parents and any other carers is of the utmost importance. It is essential that the court forms a clear assessment of their credibility and reliability. They must have the fullest opportunity to take part in the hearing and the court is likely to place considerable weight on the evidence and the impression it forms of them (see Re W and another (Non-accidental injury) [2003] FCR 346). 43. Eighth, it is common for witnesses in these cases to tell lies in the course of the investigation and the hearing. The court must be careful to bear in mind that a witness may lie for many reasons, such as shame, misplaced loyalty, panic, fear and distress, and the fact that a witness has lied about some matters does not mean that he or she has lied about everything (see R v Lucas[1981] QB 720 ). 44. Ninth, as observed by Hedley J in Re R (Care Proceedings: Causation) [2011]EWHC 1715 Fam: "